Diffuse esophageal spasm

A 60-year-old man comes to the clinic for evaluation of difficulty swallowing accompanied by chest pain. The patient had a few of these episodes in the past but did not seek treatment. The episodes occur while he is having a meal, but only occasionally. He describes difficulty in swallowing both liquids and solids. He has not noticed any pain during exertion. Medical history is noncontributory. The patient does not smoke or use illicit drugs, and he drinks alcohol socially. Temperature is 37.0°C (98.6°F), pulse is 75/min, and blood pressure is 125/85 mmHg. ECG shows no abnormalities or ischemic changes. Two subsequent troponin measurements are within normal limits. Which of the following is most likely seen in this patient on further evaluation?